Don't coerce pointers to compositor layer mappings to booleans.

Source/core/inspector/InspectorLayerTreeAgent.cpp

Index: Source/core/inspector/InspectorLayerTreeAgent.cpp
diff --git a/Source/core/inspector/InspectorLayerTreeAgent.cpp b/Source/core/inspector/InspectorLayerTreeAgent.cpp
index 1d56a28c3ec98b72066f643086df81a947df14ac..3cbe21efb3222fab65b69e2e5239e5314eac8a61 100644
--- a/Source/core/inspector/InspectorLayerTreeAgent.cpp
+++ b/Source/core/inspector/InspectorLayerTreeAgent.cpp
@@ -152,11 +152,13 @@ void InspectorLayerTreeAgent::layerTreeDidChange()
 void InspectorLayerTreeAgent::didPaint(RenderObject* renderer, GraphicsContext*, const LayoutRect& rect)
 {
     RenderLayer* renderLayer = toRenderLayerModelObject(renderer)->layer();
-    CompositedLayerMapping* compositedLayerMapping = renderLayer->compositedLayerMapping();
     // Should only happen for FrameView paints when compositing is off. Consider different instrumentation method for that.
-    if (!compositedLayerMapping)
+    // Note, that this only gets called with the FrameView's RenderView which, if it is composited, only
+    // paint into its own backing.
+    ASSERT(renderLayer->compositingState() == PaintsIntoOwnBacking || renderLayer->compositingState() == NotComposited);
+    if (renderLayer->compositingState() != PaintsIntoOwnBacking)
         return;
-    GraphicsLayer* graphicsLayer = compositedLayerMapping->mainGraphicsLayer();
+    GraphicsLayer* graphicsLayer = renderLayer->compositedLayerMapping()->mainGraphicsLayer();
     RefPtr<TypeBuilder::DOM::Rect> domRect = TypeBuilder::DOM::Rect::create()
         .setX(rect.x())
         .setY(rect.y())
@@ -179,7 +181,11 @@ PassRefPtr<TypeBuilder::Array<TypeBuilder::LayerTree::Layer> > InspectorLayerTre
 
 void InspectorLayerTreeAgent::buildLayerIdToNodeIdMap(RenderLayer* root, LayerIdToNodeIdMap& layerIdToNodeIdMap)
 {
-    if (root->compositedLayerMapping()) {
+    // The layer-id to node-id map is used later in buildObjectForLayer to map each graphics
+    // layer back to its corresponding Node. We only want to map a graphics layer to map back
+    // to the Node corresponding to its owning RenderLayer, not some other RenderLayer that
+    // paints into that GraphicsLayer.
+    if (root->compositingState() == PaintsIntoOwnBacking) {
         if (Node* node = root->renderer()->generatingNode()) {
             GraphicsLayer* graphicsLayer = root->compositedLayerMapping()->childForSuperlayers();
             layerIdToNodeIdMap.set(graphicsLayer->platformLayer()->id(), idForNode(node));